[{"type":"speech","title":"Tc(VII) immobilization on granitic rocks from \u00c4sp\u00f6 (Sweden) and Nizhnekansky massif (Russia)","issued":{"date-parts":[["2014"]]},"author":[{"family":"Totskiy","given":"Y."},{"family":"Huber","given":"F."},{"family":"Schild","given":"D."},{"family":"Sch\u00e4fer","given":"T."},{"family":"Kalmykov","given":"S."},{"family":"Geckeis","given":"H."}],"note":"TRePro III : Workshop on Modeling of Coupled Reactive Transport Processes, Karlsruhe, March 5-7, 2014 Book of Abstracts","abstract":"TRePro III \u2013 Workshop on Modelling of Coupled Reactive and Transport Processes\n1\nInstitute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT),\n2\nInstitute of Geological Sciences, Department of Earth Sciences, Freie Universit\u00e4t Berlin,\nBerlin, Germany\n3\n*\nLomonosov Moscow State University, Moscow, Russia\nCorresponding author: yuri.totskiy@kit.edu\nTechnetium-99 is one of the main long-lived component of spent nuclear fuel (SNF) with a\nhalf-life of 2.14\u00b7105years and a fission yield of ca. 6%, which possesses high mobility under\noxidizing and low solubility under reducing conditions. Information on Tc behaviour under\nconditions similar to the host rocks media around underground nuclear waste repositories is\nnecessary for disposal design.\nCrystalline rock materials from two different sites are investigated within this work. The 1st\nmaterial was obtained from \u00c4sp\u00f6 Hard Rock Laboratory (HRL) during the European project\nCROCK. It is a generic underground research laboratory (URL) for inter alia in-situ studies of\nprocesses in crystalline formations concerning deep geological disposal of spent nuclear fuel.\nDrilling of the cores were performed under anoxic conditions to preserve natural\nunderground conditions. Part of \u00c4sp\u00f6 diorite (\u00c4D) was artificially oxidized to compare with\noriginal sample. The 2nd type of rock materials is from the Nyzhnekansky (NK) granitoid\nmassif, the prospective site of nuclear waste and SNF final geological disposal. This sample\nwas drilled without special precautions and it is partially oxidized.\nIt was found, that Tc(VII) immobilization on the crystalline rocks is strongly dependent on\nsample preservation conditions \u2013 sorption values on \u00c4D are approx. 2 times higher for\nunoxidized material in comparison with oxidized one. This results can be explained by Tc(VII)\nreduction to the insoluble Tc(IV) oxide by the ferrous iron pool available in the \u00c4D. Tc(VII)\nreduction was proved by XPS and XANES analyses of granite surface after sorption. Rs values\nfor the both oxidized \u00c4D and NK materials are almost similar. Formation of the colloidal\nphase was not detected under groundwater conditions used.\nMigration study is performed on the unoxidized \u00c4D core with natural fracture. Injections of\nHTO and 36Cl show long tailing due to channeling and absence of anion exclusion. Tc\nmigration is investigated using 95mTc isotope with concentration of ~ 10-11 M. Tc recovery is\ninversely dependent on residence time in agreement with batch sorption studies, but long\ncontact time requires stop-flow experiments, which are being performed now.\n138","kit-publication-id":"220098513"}]